In the literature there has been described only one cyclic analogue of callidine, namely cyclo-/(7-glycine)-callidine/, wherein for the formation of the cycle, in contrast to the compounds of the present invention, use is made of the .alpha.-amino group of lysine, not the .omega.-amino group. No biological activity has been found for this compound. (cf. J.lieb.Ann.Chem., 691, (1966), 218-224).
The compounds according to the present invention, i.e. cyclic analogues of callidine are novel and hitherto unknown in the literature.